1. Field of the Invention
This invention relates to detergent compositions and more particularly, to detergent compositions which have good lathering ability and detergency and are mild to the skin, hair and eyes.
2. Description of the Prior Art
The sodium salts of secondary amidoamino acids of the following general formula (I') called imidazoline-type amphoteric surface active agents have been hithertofore used as a main detergent active ingredient such as of baby shampoos or bathing agents because of the low irritativeness against the skin and eyes, ##STR2## in which R.sub.1 represents an alkyl group, a hydroxyalkyl group, an aralkyl group or an alkenyl group each having from 7 to 23 carbon atoms.
However, this sodium salt of the secondary amidoamino acid is not always better than ordinary anionic surface active agents such as alkylsulfates and alkyl ether sulfates with respect to detergency and lathering ability, and have not been widely used as a detergent.
The sodium salt of the secondary amidoamino acid has large amounts of water-soluble inorganic salts such as common salt by-produced at the time of the preparation, so that when it is used as a base of liquid shampoos, it becomes difficult to thicken or condition of the shampoo. In order to permit the liquid to be thickened or conditioned, various water-soluble polymers are ordinarily used. Most of these polymers are insoluble in a concentrated salt solution, so that it is difficult to formulate into aqueous liquid detergents together with known sodium salts of secondary amidoamino acids containing large amounts of inorganic salts.